I don’t like most formula’s that are marketed for senior dogs, same as Marie said. They don’t usually meet the protein requirements for senior dogs. I do agree that Orijen Senior is probably the best one out there.
I usually recommend an all life stages food for customers at my job with senior dogs. One with high protein as well. I’d look for an all life stages food that comes in over 30% protein with the first three ingredients being whole meats and meat meals to unsure the protein is coming from animals and not plants. Some foods will have glucosimine and chondroitin in them, which is something else you can look for. Otherwise I’d suggest a supplement like NaturVet Arthrisoothe GOLD, which has Boswellia in it that is suppose to be really good for arthritic dogs.
http://www.chewy.com/dog/naturvet-arthrisoothe-gold-hip-joint/dp/48764
